We propose to determine the distinct biological and chemical properties, and to pharmacologically manipulate the actions and synthesis of thromboxanes, endoperoxides, and prostaglandins in several biological systems: 1. We specifically intend to analyze the sequence of events during platelet aggregation by the simultaneous measurement of: a) formation and effect of endoperoxides, thromboxanes, and prostaglandins, b) ADP release, c) aggregation, and d) cyclic nucleotide changes. In addition wit some unique pharmacological tools we plan to characterize the selectivity of responsiveness of ADP, endoperoxide, thromboxane and drug receptors on platelets. We also plan to evaluate bleeding disorders involving platelets. 2. We propose to study the biosynthesis and biological effects of endoperoxides and thromboxanes in a) vascular smooth muscle, especially coronary and umbilical arteries, b) spleen and c) lung. 3. We propose to characterize some previously unidentified endogenous (cardiac, renal and pulmonary) products related to prostaglandins which have unique chemical and biological properties. 4. We propose to study the properties, morphological localization, and regulation of the enzymes involved in the biosynthesis of thromboxanes, endoperoxides and prostaglandins.